Method of cord construction



J. EAGLESON Filed April 20, 1955 April 13, 1937.

N VENTOR.

COBZZGLEJO/V.

EEHHHMHH/HHWWF/ii V II! Iii!!!) ATTORNEYS Patented Apr. 13, 1937 UNITEDSTATES PATENT OFFICE METHOD OF CORD CONSTRUCTION Application April 20,1935, Serial No. 17,425

6 Claims.

whereby voids can be readily formed between the conductors so as topermit the insulation surrounding the conductors to be easily andquickly split apart. A further object of the invention is to provide avoid in the insulating material between a pair of conductorssimultaneously with the extrusion of the insulating material around theconductors. A further object is to provide a method in which a void isformed in the mass of insulation surrounding a pair of conductors and tointroduce, during the formation of such void, a liquid to prevent theadhesion of the walls thereof during and subsequent to the formation ofthe void.

The above and other objects will be apparent from the followingspecification. when read in connection with the accompanying drawing.

In the drawing- Fig. 1 is a horizontal section through suitableapparatus for carrying out my invention; Fig. 2 is a sectional viewtaken on line 2-2 of Fig. 1; Fig. 3 is a perspective View of a multiplecord construction embodying the invention; Fig. 4 is an enlarged crosssection through a multiple electric cord made according to theinvention.

In the drawing, I0 represents a die which has an outlet opening [2therein, the inner portion of which is flared to form a throat 14 intowhich projects a guide Hi. The die l0 and guide l6 form parts of astandard type of extrusion apparatus which is adapted to receive a massof plastic substance such as rubber. In this type of apparatus, suitablemeans are provided for exerting a pressure on the mass of rubber andthus force the mass out through the annular throat l4. In order to adaptthe apparatus for the practice of my improved method, I have modifiedthe standard type of machine by providing at the forward end thereof atongue l8 having a duct 20 formed therein. The outer end of the tongueprojects a short distance beyond the outer face of the die ID.

The guide is provided with longitudinally extending passageways 22-22through which are led the conductors. 24-24 which have previously beencovered with a light cotton serving 26.

Communicating with the hollow tongue 18, there is a pipe 28 leading to asupply of liquid.

In the practice of my improved method, a pair of covered conductors 24are fed through the passageways 22 while the mass of rubber or similarinsulating material is extruded through the annular throat l4. The widthof the tongue I8 is slightly less than the width of the minor axis ofthe throat I4. Thus as the material is extruded through the die alongitudinally extending void, such as indicated at 30, will be formedin the mass of insulation, this void being closed by the thin portions32-32 of the body of insulation 34, as indicated in Fig. 4.

An important feature of my improved method resides in the introductionof a liquid into the void simultaneously with the extrusion of the massof insulating material for the express purpose of preventing theadhesion of the walls of the void during the formation thereof as Wellas after curing the mass. After the product has been extruded, the sameis subjected to the action of a suiiicient degree of heat to cure theproduct and such heating is also effective to free the void of theliquid filling. When the mass is of rubber, the vulcanizing temperatureis suflicient to cause absorption of the liquids used by the rubber.

The insulating material used for encasing the conductors is preferablyrubber or similar plastic material, which lends itself to extrusion andsubsequent curing by vulcanization. Instead of rubber, it is to beunderstood of course that similar material, such as balata, guttapercha, or other rubber-like compounds may be utilized. The liquidintroduced into the void to prevent adhesion is preferably one whoseboiling point is lower than the temperature required to vulcanize theproduct so that the heat of vulcanization will not cause the formationof blisters. I also preferably use a liquid which may be substantiallyor approximately all absorbed by the plastic mass during the vulcanizingof the product so that, upon completion of the vulcanizing treatment,the 'void is substantially emptied and the walls thereof are practicallydry. Various liquids may be used for this purpose, but in practice Ihave found that a mixture of triethylene glycol and diethyl phthalategive satisfactory results. After vulcanization of the product, the samecan be readily ripped apart for a desired length, so as to causesplaying or separation of the conductors near the ends thereof, asillustrated in Fig. 3 so that the exposed conductors 24 may be readilyattached to binding screws or the like at spaced points.

While I have illustrated the method as ap plied to the production of atwo conductor cord, it is clear that the method may be employed toproduce a void or voids in a mass of insulation having various numbersof individual conductors embedded therein.

While I have described quite precisely the steps followed in thepractice of my improved method, it is to be understood that thedescription and drawing are to be interpreted in an illustrative ratherthan a limiting sense and the appended claims are to be construed asbroadly as is consistent with the prior art.

What I claim is:

1. In the manufacture of insulated electric conductors, the method whichcomprises extruding a plastic mass while feeding a pair of conductors inthe direction of the advance of the mass, simultaneously forming alongitudinally extending void in the mass between the conductors andconcurrently introducing a liquid into such void to prevent adhesion ofthe walls thereof.

2. In the manufacture of insulated electric conductors, the method whichcomprises eXtruding a plastic mass while feeding a pair of conductors inthe direction of the advance of the mass, simultaneously forming alongitudinally extending void in the mass between the conductors andconcurrently introducing a liquid into such void to prevent adhesion ofthe walls thereof and causing said liquid to be absorbed by the mass.

3. In the manufacture of insulated electric conductors, the method whichcomprises extruding a plastic mass while feeding a pair of conductors inthe direction of the advance of the mass simultaneously forming alongitudinally extending void in the mass between the conductors andconcurrently introducing a liquid into such void to prevent adhesion ofthe walls thereof, subjecting the mass to a temperature below theboiling point of said liquid and thus causing the absorption of theliquid by the mass.

4. In the manufacture of insulated electric conductors, the method whichcomprises extruding a rubber mass around a pair of conductors, whileforming a closed longitudinal void between them, introducing a liquidinto the void during its formation to prevent adhesion of the wallsthereof, and causing the absorption of the liquid by vulcanization ofthe mass.

5. In the manufacture of insulated electric conductors, the method whichcomprises extruding a mass of rubber around a plurality of conductorswhile forming a closed void between them and introducing a liquid intothe void during its formation, which liquid is capable of absorption bythe rubber mass when subjected to a temperature sufhcient to vulcanizethe mass, and vulcanizing the thus formed product so as to cause suchabsorption of the liquid by the mass.

6. In the manufacture of insulated electric conductors, the method whichcomprises extruding a mass of rubber around a plurality of conductorswhile forming a closed void between them and introducing a liquidmixture of triethylene. glycol and diethyl phthalate into the voidduring its formation, which liquid is capable of absorption by therubber mass when subjected to a temperature sufiicient to vulcanize themass, and vulcanizing the thus formed product so as to cause suchabsorption of the liquid by the mass.

JACOB EAGLESON.

